LED drive circuit and LED illumination unit

Abstract

There is provided an LED drive circuit that can be connected to an alternating-current power supply through a phase control dimmer and that drives an LED load, the LED drive circuit including: an LED current control circuit; a capacitance component and a resistance component that are connected in series between an input of the LED current control circuit and a reference potential; a switch element that is connected to both ends of the resistance component; and a switch control portion that turns off the switch element for a given period of time after a timing when the phase control dimmer is turned on and that turns on the switch element after the given period of time elapses.

Description

[0001]This application is based on Japanese Patent Application No. 2011-262481 filed in Japan on Nov. 30, 2011, the contents of which are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to an LED drive circuit and an LED illumination unit.[0004]2. Description of the Related Art[0005]LEDs have features such as a low current consumption and a long life; they are used not only for display devices but also for illumination devices and the like, and the number of the applications of LEDs is being increased. In an LED illumination device, in order to obtain a desired illumination, a plurality of LEDs are often used (for example, see JP-A-2006-319172).[0006]A general illumination device often uses an AC 100V commercial power supply; with consideration given to a case, for example, where an LED illumination unit is used instead of a general illumination unit such as an incandescent bulb, as with the general illum...

AI Technical Summary

Benefits of technology

The present invention provides an LED drive circuit and an LED illumination unit that can reduce the flickering of an LED. This is achieved by reducing the resonance phenomenon while the phase control dimmer is turned on, which prevents malfunctions and ensures stable LED current control. The switch element is turned off for a given period of time after the timing when the phase control dimmer is turned on, and then the switch element is turned on for another period of time. This cycle of turning on and off the switch element prevents the turning off of the phase control dimmer and reduces flickering of the LED.

Problems solved by technology

It is known that, even when a phase control dimmer performs light control on an incandescent bulb, an incandescent bulb whose wattage is low is connected to a dimmer, and thus flickering or flashing occurs, with the result that the light control cannot be properly performed.

Here, the timing when the triac Tri is turned on is not stabilized every half period of the alternating current, and thus energy supplied to the LED load 400 is not stabilized, with the result that flickering occurs in the LED load 400.

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